Roadwork is typically carried out by working machines that carry one or more working components and travel along a roadway. One such working machine is a milling machine or cold planer, a wheeled or track-driven vehicle that is provided with a rotating working drum that includes a plurality of cutting teeth. The drum is mounted in a housing on the frame of the machine and adapted to be lowered into contact with the road surface and rotated about a generally horizontal axis so as to cut into the surface to a desired depth as the machine is advanced along the roadway. Generally, a cold planer also includes a conveyor system that is designed to carry the milled material which has been cut from the roadway by the rotating drum to a location in front of, to the rear of, or beside the machine for deposit into a truck for removal from the milling site. One or more spray assemblies are typically mounted over the conveyors and inside the drum housing so that water may be sprayed to control the dust and heat that is generated in the milling process. If the machine is used for cold in-place recycling (as described hereinafter), a second spray assembly may be provided to spray asphalt cement onto the milled material on the roadway. Steerable track or wheel drive assemblies are provided to drive the machine and to steer it in a desired working direction. Power for driving the machine and for operating its systems is typically provided by a diesel engine.
Another type of working machine is a road stabilizer/reclaimer machine. This machine is similar to a cold planer in that it comprises a wheeled or track-driven vehicle that includes a milling assembly comprising a milling drum with a plurality of cutter teeth mounted thereon which is contained within a milling enclosure or chamber. However, the milling drum of a road stabilizer/reclaimer machine is generally employed to mill or pulverize an existing road bed or roadway to a greater depth than does a cold planer prior to repaving (usually called reclaiming) or prior to initial paving (usually called stabilizing), and it leaves the pulverized material in place. A water spray assembly, similar to that provided in a cold planer, is provided to control the dust and heat that is generated in the milling or pulverizing process. If the machine is used for cold in-place recycling (as described hereinafter), a second spray assembly may be provided to spray asphalt cement onto the pulverized material.
When a milling or stabilizing operation has been completed, paving of the roadway with asphalt paving material is generally carried out by an asphalt paving machine, another working machine. An asphalt paving machine is supplied with asphalt paving material by a number of supply trucks and/or a material transfer vehicle. The paving machine is self-propelled and driven by a wheeled or track drive system. In a common type of paving machine, an asphalt receiving hopper is located at the front end of the machine to receive asphalt paving material from a truck or material transfer vehicle, and a hopper conveyor located below the asphalt receiving hopper transfers the asphalt paving material from the hopper to a distributing assembly comprising a transverse distributing auger that is mounted near the rear of the machine. The asphalt paving material is deposited onto and across the roadway or other surface to be paved by the distributing auger, and a floating screed located at the rear end of the machine behind the distributing auger compacts the asphalt paving material to form an asphalt mat.
It is frequently desirable to apply asphalt cement or a similar substance (commonly referred to as “tack” or “tack material”) onto the surface of the roadway prior to distributing and compacting the asphalt paving material into a mat to assist in binding the asphalt paving material to the underlying surface. Tack is typically sprayed onto the surface to be paved from a spray assembly that extends transversely across the surface to be paved. Some asphalt paving machines include a tack spray assembly that is adapted to deposit tack material onto the surface of the roadway ahead of the distributing auger. Sometimes the tack material is applied by another working machine, a tack distributor truck that travels ahead of the asphalt paving machine.
Cold in-place recycling (“CIR”) equipment can be used to repair damage to a roadway in a single pass, while reusing essentially all of the existing asphalt paving material. In the CIR process, damaged layers of asphalt pavement are removed. The removed material is processed and replaced on the roadway and then compacted. If a roadway has good structural strength, a CIR process can be effective for treating all types of cracking, ruts and holes in asphalt pavement. CIR can be used to repair asphalt roadways damaged by fatigue (alligator) cracking, bleeding (of excess asphalt cement), block cracking, corrugation and shoving, joint reflective cracking, longitudinal cracking, patching, polished aggregate, potholes, raveling, rutting, slippage cracking, stripping and transverse (thermal) cracking. The root cause of the pavement failure should always be investigated to rule out base failure. However, CIR can almost always be used when there is no damage to the base of the roadway. Generally, CIR is only half as expensive as hot mix paving (i.e., paving with new asphalt paving material) while providing approximately 80% of the strength of hot mix paving.
CIR can be carried out with the aid of a milling machine or a road stabilizer/reclaimer machine that has been modified by mounting a spray assembly in the milling drum housing to inject asphalt cement into the milling drum housing. The asphalt cement is then thoroughly blended with the milled material by the milling drum and can be left in a windrow or fed by the milling machine's discharge conveyor directly into an asphalt paving machine. When the CIR process is carried out with only a milling machine or stabilizer/reclaimer and an asphalt paving machine, the asphalt cement component of the mixture must be supplied from a separate supply tank truck that is coupled to the modified milling machine or road stabilizer/reclaimer machine. The asphalt cement component is drawn directly from the tank on the supply truck and metered through a flow system that is mounted on the milling machine to the spray assembly in the milling drum housing.
Sometimes the CIR process is carried out with a milling machine or stabilizer/reclaimer in train with a cold recycler machine such as the RT-500 that is made and sold by Roadtec, Inc. of Chattanooga, Tenn. The cold recycler machine may include a vibratory screen, a crusher, an onboard source of asphalt cement and a pugmill mixer. When the CIR process is carried out using a cold recycler machine, the recycled asphalt material that is milled by the milling machine is transferred to the vibratory screen and then to the crusher on the cold recycler machine, and the screened and crushed material is then mixed with asphalt cement that is dispensed by a spray assembly from an onboard supply tank into the pugmill. In either configuration of equipment used in a CIR process, the primary component of the new pavement is asphalt paving material that is already in place on the roadway. The only other component of the new pavement is the asphalt cement carried by the cold recycler machine or by a supply truck. Since the rate of advance of the equipment engaged in the CIR process is determined primarily by the rate of advance of the milling machine, it is common for all of the components of the CIR process except for the asphalt paving machine to be coupled together so as to move at the same rate during all phases of the CIR process. Such components are frequently referred to as a CIR train.
The various spray assemblies that are found on milling machines, stabilizer/reclaimer machines, asphalt paving machines, cold recycler machines and tack distributor trucks are sized to extend across the width of the working machine. Milling machines sold in the United States generally are produced in various sizes that cut a width within the range of 4-13 feet. Stabilizer/reclaimer machines sold in the United States are generally produced in various sizes that cut a width within the range of 6.5-8.5 feet. Asphalt paving machines sold in the United States are generally produced in various sizes that pave a width within the range of 8-15 feet. In addition, some milling machines and stabilizer/reclaimer machines can accommodate milling drums of different widths, and asphalt paving machines typically can be provided with distributing augers of different widths and screed extensions that increase the width of the asphalt mat they can provide.
Typical spray assemblies are configured in a single size to fit across the width of a specific working machine. Consequently, if a milling drum on a working machine is replaced with a drum of a different size, or if a screed extension is added to a working machine, the spray assembly on the working machine must be replaced. Asphalt paving machines with tack spray assemblies and movable (i.e., extendible) screed extensions may include separate tack spray assemblies that are attached to the screed extensions. It would be desirable if a spray assembly could be provided in modular form so that it could easily be configured to accommodate any desired width of a working machine. It would also be desirable if a modular spray assembly could be provided that would allow the addition and removal of modular components without removing the base portion of the spray assembly from the working machine.